low rail pressure

i got an 03 with a new motor, injectors, and airdog fuel system. the past two days the truck has been low in power and yesturday it started dyin bouyt evert 15 seconds. i put an edge insight on it and it has low rail pressure. i drove it today and was doin good then the same thang, rail pressure dropped to 2k then died. start it back it would run bout 10 secs and die. got it to oriely changed the fuel filter when i left it would build 11k pressure just pullin outa the driveway it didnt take long for the pressure to start dropping and after about 6 miles it wouldnt build over 5k even at WOT. no codes are present. any ideas would be apreciated.